Tolerable CD Variation Analyzer Using Perturbed Nominal Models Demonstrated on altPSM

At the 65 nm node and beyond, printing the dense and isolated pitches as well as the 2D patterns within tight tolerance across the full range of known process conditions becomes a major challenge, and even more critical in the context of double exposure masks. Post-OPC simulation at nominal conditions is not sufficient to accurately assess and disposition severe errors and monitor residual proximity effects and their implications such as channel length variation.

In this paper, we explore a methodology that adopts multiple simulations to model the variability in the lithography process. This approach is predicting the process behavior by the modulation of the related lithography parameters, such as: dose, focus, and overlay. The goal is to identify the unacceptable deviation of the printed image from the designed target due to process variations. The method also provides a better statistical evaluation of the quality and robustness of the implemented Resolution Enhancement Techniques (RET) & Design for Manufacturability (DfM) solution.